How to tell if your goldfish are happy and comfortable?

i have 3 common goldfish in a 5 gallon tank. yeah, i'm aware of the 10 gallon rule(10 gallons for each fish) but they are all pretty small, and i'm planning on getting a much bigger tank later on. they have a filter, gravel, and artificial plants. i'd just like to know how to tell if they are... show more i have 3 common goldfish in a 5 gallon tank. yeah, i'm aware of the 10 gallon rule(10 gallons for each fish) but they are all pretty small, and i'm planning on getting a much bigger tank later on.

they have a filter, gravel, and artificial plants.

i'd just like to know how to tell if they are happy and comfortable in their fish bowl. they're my babies ;)

thanks in advance...
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